Traditionally, magnetic devices have been fabricated by wrapping a conductor (e.g., a wire) around a core material (e.g., ferrite) that has a relatively high magnetic permeability. Recently, with the miniaturization of many electrical products, the need for compact magnetic devices has arisen. One specific compact magnetic device is a planar magnetic (PM) transformer. The PM transformer uses interconnected planar layers of electrical conductors, rather than relatively bulky wire, disposed around magnetic core material to create primary and secondary windings. PM transformers are typically used in applications such as switching power supplies that are commonly found in many consumer and industrial products.
As is the case in many electrical applications, power dissipation that generates heat in the windings and the core is a consideration when using PM devices. Excessive heat caused by such power dissipation can damage the PM device itself as well as other components or circuitry located proximate thereto. This heat is typically dissipated through the use of a heat sink attached to the outside of the PM transformer. PM transformers are advantageous in that they provide a relatively large and planar surface area to which a heat sink may be fastened. However, even if a PM transformer is fitted with the best heat sink available, the PM transformer will still generate heat that cannot be dissipated without excessive internal heating of the PM transformer because the heat sink can only reduce the external surface temperatures of the PM transformer. Accordingly, the current, and therefore the power, that may be handled by a given PM transformer having a heat sink will be reduced from the power that the same PM transformer could handle given a more effective technique of extracting heat from the device.